vndservicemanager: remove static dependency on libselinux

libselinux_vendor is part of VNDK. No need to statically link
to it anymore.

Bug: 37343404
Test: Build and boot
Test: 'vndservice list' to ensure all services are listed as before

Change-Id: I5b3151f44f7b77ce0f2ff4bba38550a3d7e35375
Signed-off-by: Sandeep Patil <sspatil@google.com>